title: Interaction between the N-terminal SH3 domain of Nck-alpha and CD3-epsilon-derived peptides: non-canonical and canonical recognition motifs.
abstract: The first SH3 domain (SH3.1) of Nckalpha specifically recognizes the proline-rich region of CD3varepsilon, a subunit of the T cell receptor complex. We have solved the NMR structure of Nckalpha SH3.1 that shows the characteristic SH3 fold consisting of two antiparallel beta-sheets tightly packed against each other. According to chemical shift mapping analysis, a peptide encompassing residues 150-166 of CD3varepsilon binds at the canonical SH3 binding site. An exhaustive comparison with the structures of other SH3 domains able and unable to bind CD3varepsilon reveals that Nckalpha SH3.1 recognises a non-canonical PxxPxxDY motif that orientates at the binding site as a class II ligand. A positively charged residue (K/R) at position -2 relative to the WW sequence at the beginning of strand beta3 is crucial for PxxDY recognition. A 14-mer optimised Nckalpha SH3.1 ligand was found using a multi-substitution approach. Based on NMR data, this improved ligand binds Nckalpha SH3.1 through a PxxPxRDY motif that combines specific stabilising interactions corresponding to both canonical class II, PxxPx(K/R), and non-canonical PxxPxxDY motifs. This explains its higher capacity for Nckalpha SH3.1 binding relative to the wild type sequence.
authors.affiliation: Instituto de Química Física Rocasolano, CSIC, Serrano-119, 28006-Madrid, Spain.
authors.forename: Clara M
authors.initials: CM
authors.lastname: Santiveri
authors.forename: Aldo
authors.initials: A
authors.lastname: Borroto
authors.forename: Luis
authors.initials: L
authors.lastname: Simón
authors.forename: Manuel
authors.initials: M
authors.lastname: Rico
authors.forename: Balbino
authors.initials: B
authors.lastname: Alarcón
authors.forename: M Angeles
authors.initials: MA
authors.lastname: Jiménez
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017252:CD3 Complex / Q000737:chemistry*; D006801:Humans; D008024:Ligands; D008213:Lymphocyte Activation; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015513:Oncogene Proteins / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D011392:Proline / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D017252:CD3 Complex; D008024:Ligands; C078332:Nck protein; D015513:Oncogene Proteins; D010455:Peptides; D011948:Receptors, Antigen, T-Cell; D011392:Proline